I have a friend on a property with cave art here in the hunter valley of Australia. We really don't do enough to preserve it at all. He's responsible and ensures no harm but it's still weird to own private land with 10k+ year old art and have no one really give a damn about it. Compare it to European attitudes, eg. Lascaux where they closed off the cave completely and only allow tourists near the modern reconstructio…
I presume the first thing to do is to record a high res 3d scan and photos of the cave, as vandals aren't the only threat (natural elements).
I guess you could take some pictures, but it's not the kind of art that really needs high res 3d scans. In this case it's more the concept of "there was a human that did something here a very long time ago", rather than how the art itself looks.
The vandalism only covered a small portion of it, but I suspect the vandals didn't even realize they were overwriting anything, since it's really not very obvious as art - it just looks like lines.